The proliferation of mobile computing devices (such as smart phones and tablet computers, etc.), has spurned development of various attachable hardware devices to provide expanded functionality. One such example is an attachable magnetic card reader device, used for reading credit or debit card information to facilitate the receipt and processing of payments. Some such reader devices can be physically and communicatively coupled to an associated mobile device using a standard 3.5 mm audio plug when inserted into the headphone port of the mobile device (e.g., smart phone). For conventional card reader devices, only unidirectional (reader device to mobile device) communication is typically supported. As such, conventional card reader devices often lack the ability to receive information from the mobile computing device, including instructions for implementing software or firmware updates.